The invention relates to the field of imaging in general, and more particularly, to ultrasound imaging.
It is known to provide ultrasound images by scanning with different types of ultrasound transducer arrangements. For example, B mode images can be produced by linear phased arrays which scan a sector of a region as shown in FIG. 1. Linear sequential arrays can also be used to scan a rectangular region, as shown in FIG. 2, by transmitting a ultrasound beam orthogonal to a face of the array to produce a scan where the width region scanned is approximately rectangular. For example, the length of the region scanned by a linear rectangular array can be equal to the length of the array. Curved arrays can also be used to provide scans resembling a trapezoidal field of view.
Also, sectored phased arrays, transesophagael sectored phased arrays, catheter mounted intracardiac sectored phased arrays, catheter mounted Intravascular Ultrasound (IVUS) circular arrays, endoscopic arrays, and laporascopic arrays have all be used to provide B-mode ultrasonic imaging.
It is also known to provide three dimensional, or volumetric, ultrasound images using two dimensional ultrasound transducer arrays. For example, U.S. Pat. No. 4,694,434 to von Ramm and Smith discloses a steered phased array acoustic imaging scanner that provides a pyramidal volumetric scan of a region using a two dimensional ultrasound transducer array. U.S. Pat. No. 5,546,807 to Oxaal et al. discloses the display of images obtained from a volumetric scanner in which slices of the region scanned can be displayed in real time. U.S. Pat. No. 5,704,361 to Seward et al. discusses a 2D ultrasound transducer array on a catheter for intracardiac and general intraluminal volumetric scanning. U.S. Pat. No. 4,596,145 to Smith and von Ramm discloses an acoustic imaging system that can provide rectilinear volumetric images using a two dimensional ultrasound transducer array.
High-speed ultrasound volumetric imaging system part I: transducer design and beam steering, IEEE Trans. Ultras. Ferro. And Freq. Control, vol. 38, pp. 100-108, 1991, by Smith, S. W., Pavy, H. E., and von Ramm, O. T., discusses Mills cross 2D arrays used to provide steered pyramidal volumetric scanning. U.S. Pat. No. 5,901,708 to Song et al. also discussed Mills cross arrays.
Method embodiments according to the invention can provide ultrasound scans using two dimensional (2D) ultrasound transducer arrays. Pursuant to these method embodiments of the invention, the 2D ultrasound transducer arrays include at least one row of ultrasound transducer elements that is configured to extend in a curved dimension of the array and at least one column of ultrasound transducer elements that is configured to extend in a linear dimension of the array. A 2D ultrasound transducer array can be used to scan by defining a sub-aperture of the 2D ultrasound transducer array that includes a plurality of ultrasound transducer elements in the curved dimension of the array and in the linear dimension of the array and exciting the ultrasound transducer elements included in the sub-aperture to generate a transmit/receive ultrasound beam.
In some embodiments according to the invention, a first apodization function is applied to at least one row of ultrasound transducer elements that extend in the curved dimension included in the sub-aperture and a second apodization function is applied to at least one column of ultrasound transducer elements that extend in the linear dimension included in the sub-aperture.
In some embodiments according to the invention, the first apodization function includes a plurality of first excitation pulses having respective amplitudes that define a first raised cosine function a respective one of which is configured to be applied to a respective one of the plurality of the ultrasound transducer elements in the at least one row of ultrasound transducer elements. The second apodization function includes a plurality of second excitation pulses having respective amplitudes that define a second raised cosine function respective ones of which is configured to be applied to respective ones of the plurality of the ultrasound transducer elements in the at least one column of ultrasound transducer elements.
In some embodiments according to the invention, the sub-aperture is defined by selecting a plurality of first ultrasound transducer elements in the at least one row of ultrasound transducer elements and selecting a plurality of second ultrasound transducer elements in the in the at least one column of ultrasound transducer elements.
In some embodiments according to the invention, the sub-aperture is a first sub-aperture, the plurality of ultrasound transducer elements is a plurality of first ultrasound transducer elements, and the transmit/receive ultrasound beam is a first transmit/receive ultrasound beam. Other embodiments further include defining a second sub-aperture of the ultrasound transducer array that includes a plurality of second ultrasound transducer elements in the curved dimension of the array and in the linear dimension of the array and exciting the plurality of second ultrasound transducer elements included in the second sub-aperture to generate a second transmit/receive ultrasound beam.
In some embodiments according to the invention, a region is scanned in three dimensions based on the first and second transmit/receive ultrasound beams. In some embodiments according to the invention, an ultrasound transducer array carrier includes a curved surface that extends in a first dimension of the 2D ultrasound transducer array carrier and a linear surface that extends in a second dimension of the 2D ultrasound transducer array carrier. A 2D ultrasound transducer array is on the carrier and extends in the first and second dimensions of the ultrasound transducer array carrier, wherein the 2D ultrasound transducer array is configured to provide a moveable sub-aperture of the 2D ultrasound transducer array that is moveable in the first and second dimensions.
In some embodiments according to the invention, the 2D ultrasound transducer array includes a plurality of spaced-apart columns of ultrasound transducer elements and a plurality of spaced-apart rows of ultrasound transducer elements to define a plurality of Mills cross arrays. In some embodiments according to the invention, the 2D ultrasound transducer array includes one column of ultrasound transducer elements and one row of ultrasound transducer elements to define a Mill cross array.
In other embodiments according to the invention, an ultrasound transducer element has a curved face that is configured to generate a transmit/receive ultrasound beam from the curved face of the ultrasound transducer element. The ultrasound transducer carrier can have a curved surface, wherein the ultrasound transducer element is on the curved surface of the ultrasound transducer carrier wherein the curved face of the ultrasound transducer element faces away from the curved surface of the ultrasound transducer carrier.
In some embodiments according to the invention, a curvature of the curved face of the ultrasound transducer element and a curvature of the curved surface of the ultrasound transducer carrier can match one another.